Pre-combustion capture of CO2 from combustible gas is typically accomplished with physical solvents. The high partial pressure of CO2 in the fuel gas stream is usually sufficient to cause significant amounts of CO2 to dissolve into the solvent without the need for a chemical reaction. For example, at 25° C., if the partial pressure of CO2 is about I MPa, about 5 wt % CO2 will dissolve in the polymeric SELEXOL™ or acid gas removal solvent that is commonly employed for low temperature CO2 absorption. Release of the CO2 can be subsequently accomplished by subjecting the solvent to temperature increase and/or pressure reduction. However, such existing solvents have drawbacks. For example existing pre-combustion solvents are water soluble, which results in low working capacity. Additionally, such existing solvents may also have high vapor pressure at elevated temperatures, requiring a lot of make-up solvent and extra energy for cooling. Some pre-combustion solvents have low CO2 solubility at elevated temperature, requiring additional energy absorbent solvents and the methods for removing CO2 from precombustion gaseous fuels may benefit from improvements.